Rotor rim construction for fixation of blades



Feb. 12, 1957 CLARK 2,781,376

ROTOR RIM CONSTRUCTION FOR FIXATION OF BLADES Filed June 29, 1955 11311611871 em /Q0 C'L/IRK M, am, 411 6 6 United rates Patent C ROTOR RIM CONSTRUCTION FOR FIXATION OF BLADES Geoifrey Clark, Hull, England, assignor to Unipnlver Limited, Hull, England, a British company Application June 29, 1955, Serial No. 518,906

Claims priority, application Great Britain July 2, 1954 3 Claims. (Cl. 241-294) This invention relates to grinding mills of the type in which a rotor, carrying on its periphery a series of blades, is disposed concentrically within a stator, having a series of complementary fixed blades mounted upon its inner periphery, and is particularly concerned with the construction of the rim of the rotor of such a mill.

In the conventional rotor, the blades slide into slots between undercut lands formed integral with the rotor rim and are retained therein against displacement parallel to the axis of rotation of the rotor by means of split collets disposed at intervals in the lands. The cutting of such a rotor rim is a rather tedious operation, not only on account of undercutting the lands, but also due to the further dissection of the lands to accommodate the split collets. Moreover, while worn blades may be replaced, worn lands can only be rejuvenated by machining the rotor rim again, which is a lengthy operation.

An object of the invention is to provide a rotor rim, the total outer surface of which is readily replaceable when worn.

According to the present invention, an improved rotor for a grinding mill includes a rotor rim having a series of slots cut therein parallel to the axis of rotation of the rotor, a detachable blade-retaining bar disposed in each slot and having a lower portion adapted to fit said slot but of a depth less than the depth of the slot, and an upper portion, of a width greater than the width of the slot, adapted to overlap the sides of blades disposed on flats between the slots, and means to secure the bladeretaining bars to the rotor rim, e. g. a plurality of screws passing through each blade-retaining bar into the rotor rim whereby said blade-retaining bars may be retained in their respective slots and said blades may be fixedly positioned upon the flats.

For maximum convenience in the construction of the rotor rim, the slots may be rectangular slots. Alternatively, since the retention of the blade-retaining bars in rectangular slots, and thereby the retention of the blades on the flats, depends entirely upon the screws passing through the blade-retaining bars, the slots may be undercut and the blade-retaining bars made of minimum diameter at a level between their upper and lower faces whereby the blade-retaining bars may be additionally retained in and by the undercut slots, thus providing an additional safety factor. The undercutting of the slots is not, however, essential to the invention, and furthermore involves an extra step in the cutting of the rotor run.

The invention will now be further described with reference to the drawings accompanying the provisional specification in which:

Fig. l is a perspective view of part of a rotor rim in accordance with the invention, and,

Fig. 2 is a sectional detail of a form of construction alternative to that shown in Fig. 1.

In Fig. 1, a rotor rim 3 is cut away at 3:2 in a series of slots of rectangular cross section in which blade-retaining bars 4 are located, the cross section of said blade- "ice retaining bars being such that a space 5 always remains between the lower surface of each blade-retaining bar and the base of each corresponding slot 3a. Blades 6 are retained in contact with tangential flats 3b by means of the overlapping portions 4a of the blade-retaining bars 4, and are further secured against displacement parallel to the axis of the rotor by means of screws 7 passing through bars 4 into the rotor rim 3. It will be appreciated that the space 5 enables blades 6 to be rigidly held in contact with the tangential flats 3b on rotation of the screws 7 to force the bars 4 deeper into the slots 3a.

In Fig. 2 wherein like numbers refer to like parts the rotor rim is provided with undercut slots 3c and the blade-retaining bars 8, corresponding to bars 4 have a minimum diameter at the level 8a, the bars increasing in diameter above and below this level. The undercut slots provide additional retaining means for the bars 3. An advantage of this form of construction is that if one of bars 8 becomes Worn upon its upper face, it may be reversed so that the worn upper face becomes the lower face and the unworn lower face becomes the upper face.

By virtue of the provision of the spaces 5 beneath the bars 4 or 8, in conjunction with the screws 7 passing through the bars, the bars 4 or 8 may be retained in the slots 3a or 3c respectively and the blades 6 etfectively secured to the rotor rim. The necessity for using split collets is dispensed with (and consequently the number of small parts required is reduced) and the cutting of the rotor rim is considerably simplified. Moreover, by replacing the original lands by blade-retaining bars in accordance with the present invention, the rotor becomes virtually indestructible since the whole of the rim surface is completely replaceable.

I claim:

1. In a grinding mill having a rotor of the type which carries on its periphery a series of blades, a rotor rim having a plurality of slots cut therein paraliei to the axis of rotation of the rotor and having a fiat between each two adjacent slots, a blade disposed on each of said flats parallel to the slots, said blade having a width adjacent to the flat substantially equal to the width of the fiat, and said blade tapering radially outwards to a width less than its width adjacent to the flat, a blade retaining bar disposed partially within each slot and having a lower portion fitting within said slot but of a depth less than the depth of the slot and an upper portion diverging radially outwards to a width greater than th width of the slot at the level of the flats the diverging portions of the bars resting upon the tapering portions of the blades, and means to secure the blade retaining bars to the rotor rim.

2. In a grinding mill having a rotor of the type carrying on its periphery a series of blades, a rotor rim having a plurality of slots of rectangular cross section cut therein parallel to the axis of the rotation of the rotor and having a fiat between each two adjacent slots, 2. blade disposed on each flat parallel to said slots, said blade having a width adjacent to the flat substantially equal to the Width of the flat and said blade tapering radially outwards to a width less than its width adjacent to the flat, a blade retaining bar disposed partially within each slot and having a lower portion of rectangular section fitting within said slot but having a depth less than the depth of the slot, and an upper portion diverging radially outwards to a width greater than the Width of the slot at the level of the flats, the diverging portions of the bars resting upon the tapering portions of the blades and a plurality of screws passing through each blade retaining bar into the rotor rim.

3. In a grinding mill having a rotor of the type which carries on its periphery a series of blades, a rotor rim 2,7e1,1re

having a plurality of laterally undercut slots cut therein parallel to the axis of rotation of the rotor and having a flat between each two adjacent slots, a blade disposed on each fiat parallel to the slots, said blade having a width adjacent to the flat substantially equal to the width of the flat and tapering radially outwards to a width less than its Width adjacent to the fiat, a blade retaining bar disposed partially within each slot and having a'lower portion diverging radially inwards to a width greater than the width of the slot at the level of the flats and fitting within said undercut slot but being of a depth less than the depth of the slot, and an upper portion diverging radially outwards to a Width greater than the width of the slot at the level of the flats, the upper diverging portions of the bars resting upon the tapering portions of the blades, and means to secure the blade-retaining bars to the rotor rim.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain a May 4, 1945 "are 

